1. Field of the Invention
The invention in general relates to thermometers for obtaining temperature measurements in potentially hostile environments, and particularly to opto-electrical apparatus for obtaining such measurements.
2. Description of the Prior Art
Diagnostic apparatus utilizes a plurality of sensors for monitoring various parameters of a system being diagnosed. For example, during on-line monitoring of a large electrical generator, various temperature measurements are required for use by a computer which performs the diagnostic analysis.
The measurement of the temperature of generator stator windings is important to the diagnostic process since a radical change in temperature due to a change in coil electrical properties may be indicative of an actual mechanical failure.
In view of the extremely high and varying electromagnetic fields caused by current through the windings, as well as voltages measurable in the tens of kilovolt range, temperature sensors are not placed directly on the windings but are located at some distance therefrom to obtain a temperature reading by secondary measurements of the cooling water or cooling gas normally passed through the windings. Under certain circumstances, due to the distant placement of the sensor and indirect temperature measurement, a dangerous winding condition may exist before detection is possible.
The present invention obviates the indirect method of obtaining temperature indications by allowing the sensor to be placed directly in contact with the stator windings even in view of the hostile environment.